Resist pattern forming method and resist material

Abstract

A polymer having a unit expressed as "--CH 2 CHR--" as well as a substituent capable of being decomposed by acid is employed as a base resin for a resist material. The resist material is further mixed with an acid generator. A resist pattern obtained by selectively exposing and developing the resist material is irradiated with light having a wavelength of not more than 300 nm under a nitrogen atmosphere. Active hydrogen at the α-position of the unit dissociates as a result to form polymer radicals, which are linked with each other in progress of a crosslinking reaction. Namely, a crosslinked structure of the polymer is formed. Consequently, a resist pattern having high dry etching resistance is completed.

I claim: 
     
       1. A method for forming a resist pattern on a surface of a target which comprises: applying a resist onto the surface of said target;   patterning said resist through selective irradiation with radiation; and   irradiating said patterned resist with light having a wavelength of not more than 300 nm in an atmosphere of non-reactive gas,   said resist containing a polymer of the repeating unit --CH 2  CHR-- and units of a monomer containing a substituent capable of being decomposed by acid, wherein the repeating unit --CH 2  CHR-- is present in an amount of at least 50% by number of said polymer,   wherein R is selected from the group consisting of hydrogen, an alkyl group, a carboxyl group, carboxylic acid ester, acetal, an alicyclic group, a group having an aromatic ring, and a group having a heterocycle or mixtures thereof,   said resist further containing an acid generator which generates acid during said irradiation,   said non-reactive gas being non-reactive with said polymer under said light.   
     
     
       2. The resist pattern forming method in accordance with claim 1, wherein said non-reactive gas is either inert gas or nitrogen gas. 
     
     
       3. The resist pattern forming method in accordance with claim 1, further comprising: heating said patterned resist during, after, or during and after said patterned resist is irradiated.   
     
     
       4. The resist pattern forming method in accordance with claim 3, wherein said resist is heated within a temperature range of 50° C. to 200° C. 
     
     
       5. The resist pattern forming method in accordance with claim 3, wherein said heating of the patterned resist is executed after said irradiation of the patterned resist. 
     
     
       6. The resist pattern forming method in accordance with claim 3, wherein said resist is heated within a temperature range below a heat decomposition temperature of said units of a monomer containing a substituent capable of being decomposed by acid. 
     
     
       7. The resist pattern forming method in accordance with claim 6, wherein said repeating unit of the formula --CH 2  CHR-- is an acrylic unit of the formula --CH 2  CH(COOR 1 )--, wherein R 1  is selected from the group consisting of hydrogen, an alkyl group, acetal, an alicyclic group, a group having an aromatic ring, a group having a heterocycle and mixtures thereof. 
     
     
       8. The resist pattern forming method in accordance with claim 7, wherein said heat decomposition temperature is at least 140° C., and said resist is heated within a temperature range of 50° C. to 140° C. 
     
     
       9. The resist pattern forming method in accordance with claim 7, wherein said substituent capable of being decomposed by acid is selected from the group consisting of a tertiary-butoxy group, an ethoxyethyl group, and mixtures thereof. 
     
     
       10. The resist pattern forming method in accordance with claim 1, wherein said repeating unit --CH 2  CHR-- is present in an amount of at least 70% by number of said polymer. 
     
     
       11. The resist pattern forming method in accordance with claim 10, wherein said repeating unit of the formula --CH 2  CHR-- is an acrylic unit of the formula --CH 2  CH(COOR 1 )--, and wherein R 1  is selected from the group consisting of hydrogen, an alkyl group, acetal, an alicyclic group, a group having an aromatic ring, a group having a heterocycle and mixtures thereof. 
     
     
       12. A method for forming a resist pattern on a surface of a target which comprises: applying a resist onto the surface of said target;   patterning said resist through selective irradiation with radiation; and   irradiating said patterned resist with light having a wavelength of not more than 300 nm in an atmosphere of a gas,   said resist containing a polymer of the repeating unit --CH 2  CHR-- and units of a monomer containing a substituent capable of being decomposed by acid, wherein the repeating unit --CH 2  CHR-- is present in an amount of at least 50% by number of said polymer,   wherein R is selected from the group consisting of hydrogen, an alkyl group, a carboxyl group, carboxylic acid ester, acetal, an alicyclic group, a group having an aromatic ring, a group having a heterocycle or mixtures thereof,   said resist further containing an acid generator which generates acid during said irradiation,   and wherein said gas used in irradiating said patterned resist is of the same type as that generated by the acid decomposition of said units of a monomer containing a substituent capable of being decomposed by acid.   
     
     
       13. The resist pattern forming method in accordance with claim 12, wherein said gas which is generated when said substituent capable of being decomposed by acid is decomposed by acid, is selected from the group consisting of carbon dioxide, isobutene, ether, ethane, propane and mixtures thereof. 
     
     
       14. The resist pattern forming method in accordance with claim 12, wherein said atmosphere is pressurized up to a pressure exceeding the ordinary pressure. 
     
     
       15. The resist pattern forming method in accordance with claim 12, further comprising: heating said patterned resist during, after, or during and after said patterned resist is irradiated.   
     
     
       16. The resist pattern forming method in accordance with claim 15, wherein said heating of the patterned resist is executed after said irradiation of the patterned resist. 
     
     
       17. The resist pattern forming method in accordance with claim 12, wherein said repeating unit --CH 2  CHR-- is present in an amount of at least 50% by number of said polymer. 
     
     
       18. The resist pattern forming method in accordance with claim 17, wherein said repeating unit --CH 2  CHR-- is present in an amount of at least 70% by number of said polymer. 
     
     
       19. A resist comprising a polymer and an acid generator, wherein said polymer has a repeating unit --CH 2  CHR-- and units of a monomer containing a substituent capable of being decomposed by acid, said repeating unit --CH 2  CHR-- being present in an amount of at least 50% by number of said polymer, wherein R is selected from the group consisting of hydrogen, an alkyl group, a carboxyl group, carboxylic acid ester, acetal, an alicyclic group, a group having an aromatic ring, a group having a heterocycle and mixtures thereof, and   wherein said acid generator is a substance which generates acid during irradiation with radiation.   
     
     
       20. The resist in accordance with claim 19, wherein said repeating unit --CH 2  CHR-- is present in an amount of at least 70% by number of said polymer.